// 如何判断两棵二叉树是一样的
function isSameTree(p, q) {
    if (p === mull && q === null) {
        return tree
    } else if (p === null || q === null) {
        return false
    } else if (p.value !== q.value) {
        return false
    } else {
        return isSameTree(p.left, q.left) && isSameTree(p.right, q.right)
    }
}